1. Field of the Invention
This invention relates to laundry machines, and more particularly, to automatic clothes washers that have a water temperature control, and to a method of controlling the water temperature.
2. Description of the Prior Art
Controlling the mixing of hot and cold water introduced into an automatic washing machine has been known for many years. By controlling the hot and cold water valves of the machine, the temperature of the mixed water may be regulated. Typically a temperature responsive switch, such as a thermostat, is located downstream of the water valves to sense the temperature of the mixed water and through appropriate control and circuit means the opening and closing of the hot and cold water valves is controlled responsive to some predetermined temperature setting of the thermostat. One such typical arrangement is shown and described in U.S. Pat. No. 2,844,320 wherein the water valves are controlled by a thermostat located along a mutual output water line to the washing machine tub. Such an arrangement, however, has been found to detrimentally affect both the thermostat and the water valves due to their excessive cycling on and off because of the rapid changes in the water temperature in the output water line.
Another arrangement that has been utilized is shown in U.S. Pat. No. 2,533,624 wherein the thermostat is located in a temperature sensing relationship with the washing machine tub which contains the mixed water. U.S. Pat. No. 2,619,284 also shows a thermostat located on the tub. Such prior arrangements, however, result in some basic difficulties. In most automatic washing machine there is an adjustment for the clothes load and therefore the level of water introduced into the tub for a given washing operation. The thermostat cannot have a fixed ideal location on the tub as the level of the mixed water varies. For instance, at low water level if the thermostat is located to sense that water, then when the machine controls are placed on the high water level fill, the thermostat does not accurately measure the incoming water when the level of water is above the thermostat location. Conversely, if the thermostat is located to measure the high water level temperature then if the machine controls are placed on the low water level, the incoming water temperature will not be sensed by the thermostat. In addition, water in the tub is poorly mixed and tends to stratify before the washer begins its agitation or washing operation. Therefore, a tub mounted thermostat might be sensing the temperature of a portion of the water in the tub that is not representative of the average temperature of the water in the tub. Another problem with the prior art arrangements is that the long time delay in the thermostat sensing the change in temperature of the relatively large volume of water in the tub does not allow for accurately controlling the water valves to regulate the mixed water temperature.
Therefore, in the prior art water temperature control arrangements for clothes washers, in the one case the control is so sensitive to changes in temperature of the mixed water leaving the water valves that the thermostat and valves excessively cycle on and off, thus detrimentally affecting the life of those components and in the other case, the sensing of the water in the tub is not accurate and maintaining the proper temperature control of the mixed water is not achieved.
By my invention, I have provided an automatic clothes washer with an improved water temperature control and method which minimizes the amount of cycling of the temperature responsive switch and the water valves while maintaining accurate control of the desired water being introduced from the valves into the clothes washer.